Abstract: Graded crushed stone is widely used as the base filler of expressway pavement. As an important means to determine the strength of subgrade soil and pavement materials, California Bearing Ratio（CBR） test can reflect the actual bearing capacity of the subgrade or pavement structure layer. Based on the particle flow software PFC^3D, the influence of mesoscopic parameters on the CBR test is studied. With the help of the force chain model in PFC^3D, the internal force evolution process of the sample is observed, and the influence of particle microscopic parameters such as particle stiffness ratio k_n/k_s, friction coefficient μ, normal bond strength T_σ and tangential bond strength S_σ on the test results is discussed. The results show that k_n/k_s has no significant effect on the CBR value, μ and T_σ both have a linear positive correlation with the CBR value. Then, the influence of normal and tangential bond strength on the CBR test results is compared using the bond strength ratio T_σ/S_σ. It is found that S_σ has a significant impact on the CBR value, it mainly determines the tangential plasticity of the contact key, whereas T_σ mainly controls its surface normal adhesion.